var WebRtcStreamer = (function() {

    /** 
     * Interface with WebRTC-streamer API
     * @constructor
     * @param {string} videoElement - id of the video element tag
     * @param {string} srvurl -  url of webrtc-streamer (default is current location)
    */
    var WebRtcStreamer = function WebRtcStreamer (videoElement, srvurl) {
        if (typeof videoElement === "string") {
            this.videoElement = document.getElementById(videoElement);
        } else {
            this.videoElement = videoElement;
        }
        this.srvurl           = srvurl || location.protocol+"//"+window.location.hostname+":"+window.location.port;
        this.pc               = null;    
    
        this.mediaConstraints = { offerToReceiveAudio: true, offerToReceiveVideo: true };
    
        this.iceServers = null;
        this.earlyCandidates = [];
    }
    
    WebRtcStreamer.prototype._handleHttpErrors = function (response) {
        if (!response.ok) {
            throw Error(response.statusText);
        }
        return response;
    }
    
    /** 
     * Connect a WebRTC Stream to videoElement 
     * @param {string} videourl - id of WebRTC video stream
     * @param {string} audiourl - id of WebRTC audio stream
     * @param {string} options -  options of WebRTC call
     * @param {string} stream  -  local stream to send
    */
    WebRtcStreamer.prototype.connect = function(videourl, audiourl, options, localstream) {
        this.disconnect();
        
        // getIceServers is not already received
        if (!this.iceServers) {
            // console.log("Get IceServers");
            
            fetch(this.srvurl + "/api/getIceServers")
                .then(this._handleHttpErrors)
                .then( (response) => (response.json()) )
                .then( (response) =>  this.onReceiveGetIceServers(response, videourl, audiourl, options, localstream))
                .catch( (error) => this.onError("getIceServers " + error ))
                    
        } else {
            this.onReceiveGetIceServers(this.iceServers, videourl, audiourl, options, localstream);
        }
    }
    
    /** 
     * Disconnect a WebRTC Stream and clear videoElement source
    */
    WebRtcStreamer.prototype.disconnect = function() {		
        if (this.videoElement?.srcObject) {
            this.videoElement.srcObject.getTracks().forEach(track => {
                track.stop()
                this.videoElement.srcObject.removeTrack(track);
            });
        }
        if (this.pc) {
            fetch(this.srvurl + "/api/hangup?peerid=" + this.pc.peerid)
                .then(this._handleHttpErrors)
                .catch( (error) => this.onError("hangup " + error ))
    
            
            try {
                this.pc.close();
            }
            catch (e) {
                // console.log ("Failure close peer connection:" + e);
            }
            this.pc = null;
        }
    }    
    
    /*
    * GetIceServers callback
    */
    WebRtcStreamer.prototype.onReceiveGetIceServers = function(iceServers, videourl, audiourl, options, stream) {
        this.iceServers       = iceServers;
        this.pcConfig         = iceServers || {"iceServers": [] };
        try {            
            this.createPeerConnection();
    
            var callurl = this.srvurl + "/api/call?peerid=" + this.pc.peerid + "&url=" + encodeURIComponent(videourl);
            if (audiourl) {
                callurl += "&audiourl="+encodeURIComponent(audiourl);
            }
            if (options) {
                callurl += "&options="+encodeURIComponent(options);
            }
            
            if (stream) {
                this.pc.addStream(stream);
            }
    
                    // clear early candidates
            this.earlyCandidates.length = 0;
            
            // create Offer
            this.pc.createOffer(this.mediaConstraints).then((sessionDescription) => {
                // console.log("Create offer:" + JSON.stringify(sessionDescription));
                
                this.pc.setLocalDescription(sessionDescription)
                    .then(() => {
                        fetch(callurl, { method: "POST", body: JSON.stringify(sessionDescription) })
                            .then(this._handleHttpErrors)
                            .then( (response) => (response.json()) )
                            .catch( (error) => this.onError("call " + error ))
                            .then( (response) =>  this.onReceiveCall(response) )
                            .catch( (error) => this.onError("call " + error ))
                    
                    }, (error) => {
                        // console.log ("setLocalDescription error:" + JSON.stringify(error)); 
                    });
                
            }, (error) => { 
                alert("Create offer error:" + JSON.stringify(error));
            });
    
        } catch (e) {
            this.disconnect();
            alert("connect error: " + e);
        }	    
    }
    
    
    WebRtcStreamer.prototype.getIceCandidate = function() {
        fetch(this.srvurl + "/api/getIceCandidate?peerid=" + this.pc.peerid)
            .then(this._handleHttpErrors)
            .then( (response) => (response.json()) )
            .then( (response) =>  this.onReceiveCandidate(response))
            .catch( (error) => this.onError("getIceCandidate " + error ))
    }
                        
    /*
    * create RTCPeerConnection 
    */
    WebRtcStreamer.prototype.createPeerConnection = function() {
        // console.log("createPeerConnection  config: " + JSON.stringify(this.pcConfig));
        this.pc = new RTCPeerConnection(this.pcConfig);
        var pc = this.pc;
        pc.peerid = Math.random();		
        
        pc.onicecandidate = (evt) => this.onIceCandidate(evt);
        pc.onaddstream    = (evt) => this.onAddStream(evt);
        pc.oniceconnectionstatechange = (evt) => {  
            // console.log("oniceconnectionstatechange  state: " + pc.iceConnectionState);
            if (this.videoElement) {
                if (pc.iceConnectionState === "connected") {
                    this.videoElement.style.opacity = "1.0";
                }			
                else if (pc.iceConnectionState === "disconnected") {
                    this.videoElement.style.opacity = "0.25";
                }			
                else if ( (pc.iceConnectionState === "failed") || (pc.iceConnectionState === "closed") )  {
                    this.videoElement.style.opacity = "0.5";
                } else if (pc.iceConnectionState === "new") {
                    this.getIceCandidate();
                }
            }
        }
        pc.ondatachannel = function(evt) {  
            // console.log("remote datachannel created:"+JSON.stringify(evt));
            
            evt.channel.onopen = function () {
                // console.log("remote datachannel open");
                this.send("remote channel openned");
            }
            evt.channel.onmessage = function (event) {
                // console.log("remote datachannel recv:"+JSON.stringify(event.data));
            }
        }
        pc.onicegatheringstatechange = function() {
            if (pc.iceGatheringState === "complete") {
                const recvs = pc.getReceivers();
            
                recvs.forEach((recv) => {
                  if (recv.track && recv.track.kind === "video") {
                    // console.log("codecs:" + JSON.stringify(recv.getParameters().codecs))
                  }
                });
              }
        }
    
        try {
            var dataChannel = pc.createDataChannel("ClientDataChannel");
            dataChannel.onopen = function() {
                // console.log("local datachannel open");
                this.send("local channel openned");
            }
            dataChannel.onmessage = function(evt) {
                // console.log("local datachannel recv:"+JSON.stringify(evt.data));
            }
        } catch (e) {
            // console.log("Cannor create datachannel error: " + e);
        }	
        
        // console.log("Created RTCPeerConnnection with config: " + JSON.stringify(this.pcConfig) );
        return pc;
    }
    
    
    /*
    * RTCPeerConnection IceCandidate callback
    */
    WebRtcStreamer.prototype.onIceCandidate = function (event) {
        if (event.candidate) {
            if (this.pc.currentRemoteDescription)  {
                this.addIceCandidate(this.pc.peerid, event.candidate);					
            } else {
                this.earlyCandidates.push(event.candidate);
            }
        } 
        else {
            // console.log("End of candidates.");
        }
    }
    
    
    WebRtcStreamer.prototype.addIceCandidate = function(peerid, candidate) {
        fetch(this.srvurl + "/api/addIceCandidate?peerid="+peerid, { method: "POST", body: JSON.stringify(candidate) })
            .then(this._handleHttpErrors)
            .then( (response) => (response.json()) )
            .then( (response) =>  {console.log("addIceCandidate ok:" + response)})
            .catch( (error) => this.onError("addIceCandidate " + error ))
    }
                    
    /*
    * RTCPeerConnection AddTrack callback
    */
    WebRtcStreamer.prototype.onAddStream = function(event) {
        // console.log("Remote track added:" +  JSON.stringify(event));
        
        this.videoElement.srcObject = event.stream;
        var promise = this.videoElement.play();
        if (promise !== undefined) {
          promise.catch((error) => {
            // console.warn("error:"+error);
            this.videoElement.setAttribute("controls", true);
          });
        }
    }
            
    /*
    * AJAX /call callback
    */
    WebRtcStreamer.prototype.onReceiveCall = function(dataJson) {
    
        // console.log("offer: " + JSON.stringify(dataJson));
        var descr = new RTCSessionDescription(dataJson);
        this.pc.setRemoteDescription(descr).then(() =>  { 
                // console.log ("setRemoteDescription ok");
                while (this.earlyCandidates.length) {
                    var candidate = this.earlyCandidates.shift();
                    this.addIceCandidate(this.pc.peerid, candidate);				
                }
            
                this.getIceCandidate()
            }
            , (error) => { 
                // console.log ("setRemoteDescription error:" + JSON.stringify(error)); 
            });
    }	
    
    /*
    * AJAX /getIceCandidate callback
    */
    WebRtcStreamer.prototype.onReceiveCandidate = function(dataJson) {
        // console.log("candidate: " + JSON.stringify(dataJson));
        if (dataJson) {
            for (var i=0; i<dataJson.length; i++) {
                var candidate = new RTCIceCandidate(dataJson[i]);
                
                // console.log("Adding ICE candidate :" + JSON.stringify(candidate) );
                this.pc.addIceCandidate(candidate).then( () =>      { console.log ("addIceCandidate OK"); }
                    , (error) => { console.log ("addIceCandidate error:" + JSON.stringify(error)); } );
            }
            this.pc.addIceCandidate();
        }
    }
    
    
    /*
    * AJAX callback for Error
    */
    WebRtcStreamer.prototype.onError = function(status) {
        // console.log("onError:" + status);
    }
    
    return WebRtcStreamer;
    })();
    
    if (typeof window !== 'undefined' && typeof window.document !== 'undefined') {
        window.WebRtcStreamer = WebRtcStreamer;
    }
    if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
        module.exports = WebRtcStreamer;
    }
    